The present invention relates to a method of controlling recording, reproduction and erase of optical records by using a laser beam, and more particularly, to an optical record recording control method suitable to effect high-density recording by performing thermal recording through the use of a laser.
Recently, with an advance in a high information oriented society, needs for a file memory of large capacity and high density have been increased and an optical recording system has been highlighted as a system which meets such needs. The optical recording system is classified into three types, that is, a reproduction dedicated type, a write-once type and a rewrite type, and each type is used in particular applications which make the most of its features. Nowadays, a file memory of computers based on a rewrite type optical disc and a document file of computers based on an optomagnetic system have been practiced and of them, the rewrite type for which the needs are high has been desired to be further increased in density.
At present, techniques of achieving high-density recording are available including narrowing the track pitch physically, increasing the line density of recording and using a laser beam of a short wavelength, and as recording system, a pit edge recording system has been known. High-density recording can be realized by using these techniques in combination. Especially when information is held at an edge portion of a recorded domain, highly accurate determination of an edge position is of significance and it is important for realization of high density to determine this position accurately. In addition, stable formation of a small magnetic domain is important for practicing high-density recording.
In the optomagnetic recording system, the shape of a magnetic domain is considered to change readily under the influence of the ambient temperature. This leads to a significant fault especially when edge recording is performed. To solve this problem, a system has been proposed wherein a predetermined test pattern is recorded on a disc and it is reproduced to obtain control information. In connection with this proposal, one may refer to a technique disclosed in, for example, JP-A-61-239441.
JP-A-3-22223 discloses an optical recording and reproduction method according to a conventional technique, in which a recording code string of a recording mark is pulsed to form a pulse train corresponding to a length of the recording code string, the length and amplitude of the pulse train are controlled in accordance with the inverted phase length of a recording code string immediately preceding that recording code string to divide the pulse train into three parts, and recording is effected by changing the pulse width of each pulse.